Casting material

ABSTRACT

An Orthopaedic Plaster of Paris bandage ( 10 ) comprising a water resistant layer of material ( 50; 60 ) on at least one face of the bandage ( 10 ) which allows the bandage ( 10 ) to be cured by water but once the bandage ( 10 ) is set, the bandage ( 10 ) is water resistant against disintegration.

This application is a national stage application, according to ChapterII of the Patent Cooperation Treaty. This application claims thepriority date of Dec. 16, 1998 for International Patent Application No.PCT/GB98/03724.

Plaster of Paris bandages are well known in the art and are generallyemployed for arthopaedic applications such as casting and splinting.

Plaster of Paris casts however are sensitive to water and patientswearing Plaster of Paris casts have to avoid rain and can not shower.

Polyurethane resin based casts have to some extent alleviated thisproblem as they are waterproof, however their cost is prohibitivelyexpensive for many people. It is also an advantage to still use Plasterof Paris casts when the injured limb being protected by the casts islikely to swell as a Plaster of Paris cast can be disintegrated bysubmerging in water.

Thus it is desirable to develop a water resistant Plaster of Paris castor splint that would overcome or at least inhibit disintegration of thePlaster of Paris in damp or wet conditions.

In the prior art many solutions have been sought, such as painting thecast after application to a patient with a waterproofing material. Thishowever involves a second step.

The addition of a water resistant agent to the Plaster of Paris duringthe manufacturing process was previously anticipated that it wouldinterfere with the adhesion of the Plaster of Paris to the substrate andalso with the setting process of the Plaster of Paris.

Surprisingly we have found however that the application of a thin waterresistant film on at least one side of the bandage results in a materialthat can be wetted as well as resulting in a water resistant cast onapplication.

It had been previously thought that on applying a water resistant filmto the bandage, that this would prevent or inhibit the bandage frombeing wetted out in order to cure the Plaster of Paris and thus it wouldbe unable to apply the bandage to a patient.

It was also believed that using a fluid vehicle that contained water toapply the water resistant layer would cause premature curing of thecast. The present invention has surprisingly found that using a fluidvehicle that does contain water may not cause significant prematurecuring of the bandage when applied according to the present invention.

According to the present invention there is provided a Plaster of Parissplint bandage comprising a flexible substrate carrying the hemi-hydrateform of calcium sulphate characterised by that the bandage has a layerof water resistant material which allows the bandage to be cured butwhen the bandage is set provides water resistance.

The materials referred to as water resistant materials, or as waterresistant agents, are defined as materials which when on the Plaster ofParis splint bandage will allow water to penetrate the water resistantmaterial in order to cure the bandage but when the bandage is set willoffer some degree of water resistance to the cured bandage.

Also according to the present invention there is provided a Plaster ofParis splint bandage comprising a flexible substrate carrying Plaster ofParis with an upper face and a lower face, wherein at least one of theupper face or the lower face comprises a layer of water resistantmaterial.

The upper face is defined as the side facing away from the limb afterapplication and the lower face is defined as the body facing side of thebandage.

Preferably the water resistant material is applied after the substrateis impregnated with Plaster of Paris. Further for ease of manufactureand use, it is preferred that the water resistant material is appliedafter the substrate is impregnated with Plaster of Paris but beforecuring and application of the bandage.

For further ease of applying the water resistant agent, or material,onto the bandage it is convenient if the water resistant material is afluid, or is contained in a fluid, to give a fluid vehicle in order toallow convenient application of the water resistant material onto thebandage. Used herein the fluid vehicle is the water resistant materialin fluid form or any fluid containing the water resistant material.

The fluid vehicle carrying the water resistant material may be appliedto the cured bandage after application to a patient but preferably thefluid vehicle carrying the water resistant material is applied duringthe manufacturing process.

Most aptly the fluid vehicle is sprayed onto the upper face during themanufacturing process, thus providing a layer of a water resistantmaterial. However any method suitable for the application of the fluidvehicle may be used, for example the bandage could be dipped into thefluid vehicle.

The fluid vehicle carrying the water resistant material may be appliedto one surface or face of the bandage, either the upper face or thelower face, or may be applied to both faces of the bandage.

Provided that the fluid vehicle can form a layer of the water resistantmaterial on, or within, the bandage, the water resistant material doesnot necessarily need to be applied to the outer layer of the bandage.Preferably however, the water resistant layer will be on an outersurface or face of the bandage.

The water resistant material is aptly applied neat, i.e. undilutedespecially if a fluid for example silane, or in the form of an emulsion,solution, mixture or suspension. The fluid vehicle may consist wholly orpartially of the water resistant material.

Any fluid vehicle, suitable to apply the water resistant material on toone or more of the surfaces of the bandage, could in fact be used. Thefluid vehicle may be water based, solvent based or a mixture thereof.This would include suspensions and emulsions.

When the fluid vehicle is an emulsion or solution, the emulsion orsolution may be prepared from any material that will form an emulsion orsolution and which forms a water resistant film on drying afterapplication of the bandage to a limb.

Typically the water resistant material may be in the form of anemulsion, solution or suspension in water. When a solvent is usedsuitable ratios of solute to solvent are typically 25% to 75%. Suitablesolvents that may be used with the present invention include alcohols,ketones, aromatic hydrocarbons, aliphatic hydrocarbons, esters andethers.

If the water resistant film is only on one side or face of the bandagethe opposite face would comprise exposed Plaster of Paris. This enablesthe Plaster of Paris to wet out quickly, as well as enabling laminationof the layers and smoothing out of the resulting cast.

If the water resistant film is on both sides it is preferable to have alower individual layer weight of the water resistant material than thatused on a bandage with only one layer of the water resistant material.This is to enable the water to migrate through the film more efficientlyand this enables the Plaster of Paris to wet out quickly, as well asenabling lamination of the layers and smoothing out of the resultingcast.

On application a water resistant upper face will preferably make up theoutside of the cast, thus resulting in a water resistant cast.

Suitably the water resistant layer comprises 1 to 25% by cast weight.The water resistant layer need not be a thick layer provided it canoffer water resistance to the bandage and therefore this layer may beless than 1% of the weight of the cast.

Water resistant bandages according to the present invention could beused for the entire cast or just to provide a layer of the waterresistant material on, or within, the cast. Therefore water resistantbandages of the present invention could be used in conjunction withordinary bandages. It is envisaged that where water resistant bandagesof the present invention are used in conjunction with ordinary bandages,the water resistant bandages will be applied as a last layer, or outerlayer, of the bandaging material making up the cast in order to give anouter water resistant layer of material to protect the cast as a whole.In this way the ordinary bandages can be used to provide a cast of therequired thickness or strength, while the water resistant bandages ofthe present invention provide water resistance to the cast.

Suitably when the fluid vehicle used contains water it will contain anamount of water less than the stoichiometric amount of water required toconvert the hemi-hydrate to dihydrate of the Plaster of Paris bandage.Where the fluid vehicle contains water it is preferred that the amountof water used is less than 0.5 mole of water per mole of hemi-hydratecalcium sulphate used in the bandage. Preferably around 0.2 of water permole of hemi-hydrate calcium hydrate used in the bandage, would be usedwhere the fluid vehicle contains water.

It is still possible to apply the water resistant material when muchlarger amounts of water, than described above, are used in the fluidvehicle to apply the water resistant layer by heating the bandage toaround 100° C., or above, and applying the fluid vehicle to the heatedbandage. The water resistant material can then be applied to the surfaceof the bandage while the water evaporates off before causing significantcuring of the bandage.

It is even possible to use copious amounts of water to apply the fluidvehicle which if did cure the bandage could be heated to a temperaturesufficient enough to convert the di-hydrate form of Plaster of Paris tothe hemi-hydrate form.

Once the water resistant material is applied to the bandage the treatedbandage, comprising at least one layer of a water resistant material,can be used before the layer of water resistant material has dried ontothe bandage. It does not necessarily matter if the layer of waterresistant material, on or within, the bandage has not dried completelybefore the bandage is immersed in water to initiate curing.Alternatively the bandage comprising a layer of water resistant materialcan be allowed to dry completely, and stored, before being applied to auser in the usual method of applying Plaster of Paris bandages. Thebandage according to the present invention can thus be supplied to theuser with the layer of water resistant material dry or wet.

Where bandages of the present invention are to be applied where thelayer of water resistant material on the bandage is still wet or atleast not completely dry, the bandage may be placed in a fluid, ormoisture, impermeable container before the layer of water resistantmaterial on the bandage is able to completely dry. The bandage may thenbe stored in the container in this wet form, or embodiment of thepresent invention, ready to be applied to a user in the usual method.The water penetration of the bandage during the curing process may alsobe made more efficient by having a wet layer of water resistantmaterial. Applying a bandage with a wet layer of water resistantmaterial may also assist with the drying of the bandage after curing.

Suitable material for the impermeable container may be any conventionalmaterial, for example, plastic film paper product, metallic foil,laminates or any other material which will be impermeable to fluids.

The container may be of any size and shape which is able to contain therequired contents. Suitable packaging to act as the container are 3dimensional bags well known in the art.

The water resistant material may be any material capable of forming awater resistant layer on, or within, the bandage. Typically the waterresistant material will be a readily available water resistant agent orpolymer.

Any suitable water resistant agent can be used, for example silicones,polyvinylchlorides, alkoxysilane resins, hydrocarbon waxes or preferablypolyvinyl acetate/acrylic acid copolymers.

Coloured dye may also be added to the fluid vehicle to produce afinished cast of a chosen colour whereby the dye may be trapped in afilm layer of the bandage. Any dye suitable to dye the finished cast maybe used. Both water soluble and water insoluble dyes could be used.Alternatively the dye need not be added to the fluid vehicle but may beadded at any other appropriate time to produce a dyed finished cast.

Water resistant Plaster of Paris splint bandages according to theinvention can be factory manufactured and supplied to the user in aready to use form whether the water resistant material on the bandage isdry or wet. When the water resistant splint bandage is factorymanufactured and supplied to a user with a wet layer of the waterresistant material it is envisaged that the bandage with its wet layerof water resistant material will be contained in a fluid impermeablecontainer at the manufacturing stage, ready for use.

Alternatively kits to produce a water resistant Plaster of Paris splintbandage from an ordinary Plaster of Paris bandage supplied with the kit,or not, can be manufactured and supplied to the user. The kits willcontain a water resistant material to be applied to an ordinary Plasterof Paris bandage, whether this is itself supplied with the kit or not,for application to the ordinary Plaster of Paris bandage to produce awater resistant Plaster of Paris splint bandage of the presentinvention. On using the water resistant Plaster of Paris splint bandagekit, the user can decide if the water resistant material applied to thebandage is to be used wet or dry. If it is to be used wet it may be usedimmediately or could be store in a fluid impermeable container. If thebandage is to used with a dry layer of water resistant material, thebandage will be required to be dried before use.

The invention will now be described by way of example only withreference to the accompanying drawings.

FIG. 1 shows a cross section of a Plaster of Paris splint bandage of theinvention.

FIG. 2 shows a cross section of the Plaster of Paris splint bandage of afurther embodiment of the invention.

FIG. 3 shows the bandage of FIG. 1 in rolled up form.

FIG. 4 shows a cross section of the Plaster of Paris splint bandage of afurther embodiment of the invention.

FIG. 1 shows a Plaster of Paris splint bandage 10 comprising a substrate20 impregnated with Plaster of Paris resulting in a layer of Plaster ofParis on the upper face 30 and lower face 40. The upper face 30additionally has a water resistant layer 50.

FIG. 2 shows a Plaster of Paris splint bandage 10 of FIG. 1 comprising asubstrate 20 impregnated with Plaster of Paris resulting in a layer ofPlaster of Paris on the upper face 30 and lower face 40. The upper face30 and lower face 40 additionally have a water resistant layer 50 and60.

FIG. 3 shows the bandage 10 in a rolled up form. The bandage can berolled with either face on the outside, depending on the applicationtechniques used by casting technicians.

FIG. 4 shows a Plaster of Paris splint bandage 10 of FIG. 1 comprising asubstrate 20 impregnated with Plaster of Paris resulting in a layer ofPlaster of Paris on the upper face 30 and lower face 40. The lower face40 additionally has a water resistant layer 70.

The invention will be further illustrated by the following furtherexamples.

Bandages

Bandages containing various water resistant agents were tested for theirwater resistance determined by measuring their Breaking Load after waterwas applied to the surface of the bandage in comparison to controls.

Plaster of Paris bandages sold under the Smith & Nephew Trade MarkGYPSONA were used. The bandages used were 6.1 m in length and 10 cm wide(0.16 m²).

The coating weight of plaster mass on the substrate was approximatelybetween 390 to 560 grams per square meter. The substrate is leno gauzeas supplied by Smith & Nephew Medical Fabrics.

All bandages were prepared by unspooling the bandage cutting to thedesired length and then respooling onto a core, then stored in aresealable bag until needed. Bandages were weighed without the corebefore being treated, and then were treated by applying the waterresistant agent to either the upper face only of the bandage or thelower face. After the water resistant material has been applied to thebandages, the bandages were reweighed to calculate the weight of thewater resistant material.

Preparation of Water Resistant Agent

Unless commercially bought in a ready to use form the fluid vehiclewhether this was water based or solvent based or a mixture thereof washeated and agitated using a hot plate stirrer. When a water resistantagent requiring dissolving was used it was first dissolved into thefluid vehicle. The required amount of water resistant agent was addedslowly to the fluid vehicle, avoiding agglomeration. When the waterresistant agent was dissolved the solution was allowed to cool to roomtemperature and then made up to volume before being stored at roomtemperature until required.

Water Resistance of Test Samples

Different water resistant agents were tested by spray application with apressure range from 17 psi to 60 psi. The spray gun was heldapproximately 5 cm in distance from the bandage when applying the waterresistance agent. The amount of water resistant agent and amount ofcoverage was as follows.

(1) One Face of Bandage Having the Dry Water Resistant Layer

The bandage was unspooled, the fluid vehicle containing the waterresistant agent was then evenly sprayed onto the whole bandage on oneside and was then left to dry. After drying the sample bandage wasweighed and then spooled on to a core and stored in a resealable baguntil required.

Bandages prepared in this way could be used when the water resistantlayer was on the inner face or the outer face of the bandage dependingon which way round the bandage was applied.

(2) One Face of Bandage Having the Wet Water Resistant Layer

The bandage was unspooled, the fluid vehicle containing the waterresistant agent was then evenly sprayed onto the whole bandage on oneside, the upper face. The treated bandage was weighed and immediatelyspooled on to a core and stored in a resealable bag, before drying,until it was required.

Preparation of Casts

The treated bandages, having at least one layer of a water resistantmaterial, stored in resealable bags were immersed in a large excess ofwater for around 6 seconds and squeezed once on removal to remove excesswater.

Once the curing process of the bandage had been initiated the roll ofbandage was formed into a 5 cm diameter by 10 cm wide cast by, unrollingthe bandage around a 5 cm diameter cylinder (mandrel). When the bandagehad been unwound the final layer was smoothed until initial settingoccurred. The bandage was then removed from the mandrel and placed atroom temperature to dry for at least three days.

Treated bandages with the upper face having a water resistant layer wereused as a last layer only on preparing some sample casts. These samplecasts were prepared using 1.4 m length of untreated bandage for theinner layers of the cast and 0.2 m length of the treated bandages, forthe last outer layer (with overlap). These casts were, similarly,removed from the mandrel and placed at room temperature to dry for atleast three days.

Water Resistance Testing of Casts

Cast samples were prepared as described above and then tested for wetstrength using a “drip test”. The “drip test” is defined by marking thecast to be tested at 90° intervals and then suspending this cast so thatwater would drip onto the cast (to mimic a shower). The sample castbeing tested was rotated by 90° each minute, for eight minutes, toinsure an even wetting of the sample while water was dripped onto thecast at a rate of 60 ml/minute. After the test period excess water wasremoved from the cast using absorbent paper and then the sample cast wastested for its breaking load, under the “crush test”.

The “crush test” is defined as follows. Using a Zwick 1464 machine thebreaking load required to reach the yield point of the cast sample wasdetermined. The samples were loaded diametrically and then compressed by8 mm. The Load Cell used was 50 kN and the test speed was 5 mm/min.

Controls

Untreated bandages were cured and applied to 5 cm diameter Mandrels toform a control cast in a similar way as for the treated bandages. Theseuntreated casts were tested for their breaking load after the drip testin order to give a comparison of breaking load.

Water Resistant Agents used Chemical Trade Name Name AbbreviationSupplier Thompsons Mixture (WP) All-purpose including an Wood organotinPVC Preserver stabiliser Yacht Varnish Oil Modified (PE) polyesterX935-19 (ICI) ICI Paints Division Middlesborough Vernish Fisch (VF) S &N Lab. Fisch — silane resin S & N GRC Blackfriar (IV) Quick DryingInterior Varnish PVP K15 Poly(vinyl (PVP) International pyrrolidone)Speciality Products PVA GL05 Poly(vinyl (PVA) Nippon Gohshei alcohol)Emultex 592 Polyvinyl Harco Chemical acetate/acrylic Co. copolymer

EXAMPLES

Each sample was tested under the above conditions.

Water Resistant Breaking Load Example Material Amount (g) ImprovementDry Water Resistant Material on Upper Face of Bandage. 1 ICI 3.7 30 2ICI 6.7 32 3 ICI 6.3 28 4 IV 3.6 16 5 Silane 0.7 27 6 PE 0.6 14 DryWater Resistant Material on Lower Face of Bandage 7 ICI 2.6 11 Dry WaterResistant Material on Upper Face of Bandage and Treated Bandage used forlast layer only. 8 ICI 24.3 69 9 PVP 19.5 24 10 IV 0.8 16 11 PE 2.1 3612 WP 15.1 27 Wet Layer of Water Resistant Material on Upper Face ofBandage. 13 50% VF 7.7 21.5 14 WP 0.66 10

Example 15

An emulsion of polyvinyl acetatelacrylic acid copolymer, available as a50% solids in emulsion sample (Emultex 592) from Chemical Co. was used.

A Plaster of Paris bandage comprising a leno gauze substrate impregnatedwith Plaster of Paris was laid out flat and sprayed on one side with theemulsion. After drying the bandage was rolled up with the layer of waterresistant material on the inside.

For application the bandage was applied using a standard technique ofdipping the rolled-up bandage into water, squeeze once and applying thebandage to a mandrel representing a limb.

In this way a water resistant splint bandage was produced.

What is claimed is:
 1. A Plaster of Paris splint bandage, comprising:(a) a flexible substrate; (b) a hemi-hydrate form of calcium sulfatecarried by said substrate, said hemi-hydrate form of calcium sulfateremaining stable when maintained in moisture-free conditions and curingupon exposure to sufficient moisture to form a rigid, self-supportingstructure; and (c) a layer of water resistant material carried by saidbandage, said water resistant material permitting subsequent exposure ofthe hemi-hydrate form of calcium sulfate to the moisture used toinitiate curing while providing water resistance to the bandage aftercuring is complete, said water resistant material being contained in afluid vehicle, wherein said fluid vehicle contains a predeterminedamount of water less than the stoichiometric amount of water required toconvert the hemi-hydrate form of calcium sulphate in the bandage to thedy-hydrate form of calcium sulphate.
 2. A Plaster of Paris splintbandage according to claim 1, wherein the layer of water resistantmaterial is wet on the bandage.
 3. A Plaster of Paris splint bandageaccording to claim 1, wherein the bandage is stored ready for use in afluid impermeable container.
 4. A Plaster of Paris splint bandageaccording to claim 1, wherein said fluid vehicle is selected from thegroup consisting of a second water resistant material, a water basedfluid, a solvent based fluid, and a mixture of water and solvent.
 5. APlaster of Paris splint bandage according to claim 1 wherein saidpredetermined amount of water comprises less than 0.5 mole of water permole of the hemi-hydrate form of calcium sulphate used in the bandage.6. A Plaster of Paris splint bandage according to claim 1, and includinga dye carried by the bandage for imparting color thereto.
 7. A Plasterof Paris splint bandage according to claim 1, wherein said fluid vehicleincludes a dye for imparting color to the bandage.
 8. A Plaster of Parissplint bandage according to claim 1, wherein the water resistantmaterial comprises between 1 and 25 percent of the total weight of thebandage.
 9. A Plaster of Paris splint bandage according to claim 1,wherein the water resistant material comprises a polymer selected fromthe group consisting of Poly(vinyl pyrrolidone) and Poly(vinyl acetate).10. A method of manufacture of a water resistant Plaster of Paris splintbandage, comprising the steps of: (a) providing a bandage including aflexible substrate carrying a hemi-hydrate form of calcium sulfatethereon, said hemi-hydrate calcium sulfate remaining stable whenmaintained in moisture-free conditions and curing upon exposure tosufficient moisture to form a rigid, self-supporting structure; and (b)applying a layer of water resistant material to said bandage prior toexposure of the hemi-hydrate form of calcium sulfate to the moisture toinitiate curing thereof, said water resistant material imparting waterresistance to the bandage after curing is complete, said water resistantmaterial being contained in a fluid vehicle, wherein said fluid vehiclecontains a predetermined amount of water less than the stoichiometricamount of water required to convert hemi-hydrate form of calciumsulphate in the bandage to the di-hydrate form of calcium sulphate. 11.A water resistant splint bandaging system, comprising: (a) a Plaster ofParis splint bandage carrying a hemi-hydrate form of calcium sulfatethereon adapted for remaining stable when maintained in moisture-freeconditions and curing upon exposure to sufficient moisture to form arigid, self-supporting structure; and (b) a water resistant material forbeing applied in a layer to said bandage prior to exposure of thebandage to the moisture, said water resistant material imparting waterresistance to the bandage after curing is complete, said water resistantmaterial being contained in a fluid vehicle, wherein said fluid vehiclecontains a predetermined amount of water less than the stoichiometricamount of water required to convert the hemi-hydrate form of calciumsulphate in the bandage to the di-hydrate form of calcium sulphate. 12.A water resistant splint bandaging system according to claim 11, whereinthe water resistant material is contained in a spray.
 13. A waterresistant splint bandaging system according to claim 11, wherein thewater resistant material comprises a polymer selected from the groupconsisting of Poly(vinyl pyrrolidone) and Poly(vinyl acetate).
 14. Awater resistant splint bandaging system according to claim 11, whereinthe water resistant material comprises between 1 and 25 percent of thetotal weight of the bandage.
 15. A water resistant splint bandagingsystem according to claim 11, and including a dye carried by the bandagefor imparting color to the bandage.